1. Field of the Invention
This invention relates generally to a method and apparatus for forming a head on a fastener, and more particularly to a method and apparatus for axially compressing an end portion of a wire so as to outwardly expand a predetermined amount of wire material and thereby form a head on the wire wherein the shape of the head is controlled by directing the flow of the wire material during the axial compression thereof.
2. Description of the Related Art
Typically, to form a fastener such as a nail, an end portion of a wire is axially compressed with a punch or the like with sufficient force so as to expand the end portion of the wire radially outwardly and thereby form a head thereon. The opposite end of the wire is then formed into a point so as to provide the finished nail.
During axial compression of the wire, the wire material tends to randomly expand outwardly without control. This random expansion typically results in a nail head that is slightly out of round and/or off-center with respect to the central axis of the wire shank, as illustrated in FIG. 6. Such a nail can be a problem when utilized in a power nailer causing tumbling or jamming of the nails therein.
It therefore would be desirable to provide a method and apparatus for axially compressing an end portion of a wire so as to expand a predetermined amount of wire material radially outwardly in a controlled manner and thereby form a head on the wire wherein the shape of the head is consistent from part to part and is consistently centered with respect to a central axis of the wire.